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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.awt.geom;

import java.lang.annotation.Native;

/**
 * The <code>PathIterator</code> interface provides the mechanism
 * for objects that implement the {@link java.awt.Shape Shape}
 * interface to return the geometry of their boundary by allowing
 * a caller to retrieve the path of that boundary a segment at a
 * time.  This interface allows these objects to retrieve the path of
 * their boundary a segment at a time by using 1st through 3rd order
 * B&eacute;zier curves, which are lines and quadratic or cubic
 * B&eacute;zier splines.
 * <p>
 * Multiple subpaths can be expressed by using a "MOVETO" segment to
 * create a discontinuity in the geometry to move from the end of
 * one subpath to the beginning of the next.
 * <p>
 * Each subpath can be closed manually by ending the last segment in
 * the subpath on the same coordinate as the beginning "MOVETO" segment
 * for that subpath or by using a "CLOSE" segment to append a line
 * segment from the last point back to the first.
 * Be aware that manually closing an outline as opposed to using a
 * "CLOSE" segment to close the path might result in different line
 * style decorations being used at the end points of the subpath.
 * For example, the {@link java.awt.BasicStroke BasicStroke} object
 * uses a line "JOIN" decoration to connect the first and last points
 * if a "CLOSE" segment is encountered, whereas simply ending the path
 * on the same coordinate as the beginning coordinate results in line
 * "CAP" decorations being used at the ends.
 *
 * @author Jim Graham
 * @see java.awt.Shape
 * @see java.awt.BasicStroke
 */
public interface PathIterator {

  /**
   * The winding rule constant for specifying an even-odd rule
   * for determining the interior of a path.
   * The even-odd rule specifies that a point lies inside the
   * path if a ray drawn in any direction from that point to
   * infinity is crossed by path segments an odd number of times.
   */
  @Native
  public static final int WIND_EVEN_ODD = 0;

  /**
   * The winding rule constant for specifying a non-zero rule
   * for determining the interior of a path.
   * The non-zero rule specifies that a point lies inside the
   * path if a ray drawn in any direction from that point to
   * infinity is crossed by path segments a different number
   * of times in the counter-clockwise direction than the
   * clockwise direction.
   */
  @Native
  public static final int WIND_NON_ZERO = 1;

  /**
   * The segment type constant for a point that specifies the
   * starting location for a new subpath.
   */
  @Native
  public static final int SEG_MOVETO = 0;

  /**
   * The segment type constant for a point that specifies the
   * end point of a line to be drawn from the most recently
   * specified point.
   */
  @Native
  public static final int SEG_LINETO = 1;

  /**
   * The segment type constant for the pair of points that specify
   * a quadratic parametric curve to be drawn from the most recently
   * specified point.
   * The curve is interpolated by solving the parametric control
   * equation in the range <code>(t=[0..1])</code> using
   * the most recently specified (current) point (CP),
   * the first control point (P1),
   * and the final interpolated control point (P2).
   * The parametric control equation for this curve is:
   * <pre>
   *          P(t) = B(2,0)*CP + B(2,1)*P1 + B(2,2)*P2
   *          0 &lt;= t &lt;= 1
   *
   *        B(n,m) = mth coefficient of nth degree Bernstein polynomial
   *               = C(n,m) * t^(m) * (1 - t)^(n-m)
   *        C(n,m) = Combinations of n things, taken m at a time
   *               = n! / (m! * (n-m)!)
   * </pre>
   */
  @Native
  public static final int SEG_QUADTO = 2;

  /**
   * The segment type constant for the set of 3 points that specify
   * a cubic parametric curve to be drawn from the most recently
   * specified point.
   * The curve is interpolated by solving the parametric control
   * equation in the range <code>(t=[0..1])</code> using
   * the most recently specified (current) point (CP),
   * the first control point (P1),
   * the second control point (P2),
   * and the final interpolated control point (P3).
   * The parametric control equation for this curve is:
   * <pre>
   *          P(t) = B(3,0)*CP + B(3,1)*P1 + B(3,2)*P2 + B(3,3)*P3
   *          0 &lt;= t &lt;= 1
   *
   *        B(n,m) = mth coefficient of nth degree Bernstein polynomial
   *               = C(n,m) * t^(m) * (1 - t)^(n-m)
   *        C(n,m) = Combinations of n things, taken m at a time
   *               = n! / (m! * (n-m)!)
   * </pre>
   * This form of curve is commonly known as a B&eacute;zier curve.
   */
  @Native
  public static final int SEG_CUBICTO = 3;

  /**
   * The segment type constant that specifies that
   * the preceding subpath should be closed by appending a line segment
   * back to the point corresponding to the most recent SEG_MOVETO.
   */
  @Native
  public static final int SEG_CLOSE = 4;

  /**
   * Returns the winding rule for determining the interior of the
   * path.
   *
   * @return the winding rule.
   * @see #WIND_EVEN_ODD
   * @see #WIND_NON_ZERO
   */
  public int getWindingRule();

  /**
   * Tests if the iteration is complete.
   *
   * @return <code>true</code> if all the segments have been read; <code>false</code> otherwise.
   */
  public boolean isDone();

  /**
   * Moves the iterator to the next segment of the path forwards
   * along the primary direction of traversal as long as there are
   * more points in that direction.
   */
  public void next();

  /**
   * Returns the coordinates and type of the current path segment in
   * the iteration.
   * The return value is the path-segment type:
   * SEG_MOVETO, SEG_LINETO, SEG_QUADTO, SEG_CUBICTO, or SEG_CLOSE.
   * A float array of length 6 must be passed in and can be used to
   * store the coordinates of the point(s).
   * Each point is stored as a pair of float x,y coordinates.
   * SEG_MOVETO and SEG_LINETO types returns one point,
   * SEG_QUADTO returns two points,
   * SEG_CUBICTO returns 3 points
   * and SEG_CLOSE does not return any points.
   *
   * @param coords an array that holds the data returned from this method
   * @return the path-segment type of the current path segment.
   * @see #SEG_MOVETO
   * @see #SEG_LINETO
   * @see #SEG_QUADTO
   * @see #SEG_CUBICTO
   * @see #SEG_CLOSE
   */
  public int currentSegment(float[] coords);

  /**
   * Returns the coordinates and type of the current path segment in
   * the iteration.
   * The return value is the path-segment type:
   * SEG_MOVETO, SEG_LINETO, SEG_QUADTO, SEG_CUBICTO, or SEG_CLOSE.
   * A double array of length 6 must be passed in and can be used to
   * store the coordinates of the point(s).
   * Each point is stored as a pair of double x,y coordinates.
   * SEG_MOVETO and SEG_LINETO types returns one point,
   * SEG_QUADTO returns two points,
   * SEG_CUBICTO returns 3 points
   * and SEG_CLOSE does not return any points.
   *
   * @param coords an array that holds the data returned from this method
   * @return the path-segment type of the current path segment.
   * @see #SEG_MOVETO
   * @see #SEG_LINETO
   * @see #SEG_QUADTO
   * @see #SEG_CUBICTO
   * @see #SEG_CLOSE
   */
  public int currentSegment(double[] coords);
}
